As the parent post mentions, it's also about moving your costs from a mix of capital and operating to 100% operating. This is one of the arguments that has motivated Netflix' move to AWS (and it makes sense for other SaaS): their costs scale more or less directly with their customer base, and thus revenue, with no up-front capital required.

See http://qconsf.com/dl/qcon-sanfran-2010/slides/AdrianCockcrof... for more.